My 2001 mazda 323 will travel nicely on hot day in particular then all of a sudden cough cough stop. There is no raise in temp on dial. Open the bonnet wait 15 minutes try again car goes for another 30 minutes as the first time then splutters and stops. The high outside temperature tends to facilitate problem. The computer read out shows nothing at 2 different garages. One guy thought it might be fuel pump, replaced that and it still does it.I, m too scared to drive car, what say this happens in a 5 km tunnel, i'm at a wits end please help. The last guy said there was nothing wrong with car Yeah Right.